Post by brobear on Apr 3, 2018 3:20:14 GMT -5
markgelbart.wordpress.com/2011/03/10/pleistocene-bears-of-southeastern-north-america/
Pleistocene Bears of Southeastern North America
Nothing demonstrates wilderness more than a robust population of free roaming bears. During the Pleistocene before people were around to kill them and destroy their habitat, there must have been tens of thousands of bears living within the boundaries of what today is Georgia. It’s possible that 5 different species could have been found here in the same time span, though we can be more sure there were at least 3 sharing the same range. Today, only 1 species of bear resides in Georgia–an estimated 5100 black bears still roam the mountains, the Okefenokee Swamp, the Altamaha and Ocmulgee river bottoms, and Houston County. Occasional stragglers leave these last strongholds and raid urban dumpsters and suburban bird feeders, but these occurrences are rare. One study of Georgia bears determined that suitable habitat can support 1 bear for every 3 square kilometers. That means ideally, Pleistocene Georgia hosted a population of 30,000-40,000 bears. (*Georgia is about 60,000 square miles. 1.86 square miles =3 square kilimeters. Moreover, during stadials Georgia’s land mass increased by about 10,000 square miles due to the fall in sea level.)
Here’s a review of every known bear species that lived during the Pleistocene in southeastern North America.
Black bear–Ursus americanus
Ursus abstruscus is the probable evolutionary ancestor of American and Asian black bears which once consisted of a geographically continuous population. Glacial ice separated the two populations at the beginning of the Pleistocene, resulting in two different species. Bjorn Kurten notes that Pleistocene black bears grew as large as modern day grizzlies. I believe Pleistocene black bears were larger and fiercer than their modern day descendents because they had to survive confrontations with saber-tooths, giant panthers, jaguars, and packs of dire wolves. Cavers and scientists discovered black bear fossils at Ladds and Kingston Saltpeter Cave in Bartow County, and the Isle of Hope Site in Chatham County. They’re also commonly found in Florida fossil sites but only a few have been recorded from South Carolina.
Florida spectacled bear–Tremarctos floridanus
Now extinct, this was likely the second most common species of bear in southeastern North America during the Pleistocene. Only 1 specimen has ever been recovered in Georgia (at Ladds), but its fossils have commonly been found in Florida and South Carolina. It’s thought of as primarily a vegetarian, but a recent study of Pleistocene bears concluded that all were opportunistic omnivores that would eat anything they could obtain. Tremarctos’s range in the late Wisconsinian Ice Age seems to have been restricted to the southeast. During warm interglacials it expanded as far north as Kentucky. It probably just lived in the coastal plain of Georgia and South Carolina as well as Florida during colder climatic stages.
Lesser short-faced bear–Arctodus pristinus
It’s unclear from the fossil record whether this species co-existed with its larger cousin, the giant short-faced bear, or was simply ancestral to it. Its fossils have only been recovered from a few eastern sites in Florida, South Carolina, Maryland, and West Virginia. Teeth attributed to this species overlap in size with those of Arctodus simus. Florida fossils of this species, including those from Leisey Shell Pit, indicate this animal lived from the early to mid-Pleistocene (~1.8 million-300,000 BP), whereas giant short-faced bear fossils in Florida date to the late Pleistocene (~300,000-~11,000 BP). However, fossils of the lesser short-faced bear were found in South Carolina sediments thought to date from the Sangamonian Interglacial (~132,000-~118,000 BP) which is also considered late Pleistocene. These South Carolina specimens haven’t been radiometrically dated, so no one knows exactly how old they are. Perhaps this species did survive as a relic species in some geographical locations until the megafauna extinction. Arctodus pristinus is considered more of a general feeder; Tremarctos floridanus a more herbivorous species; Arctodus simus a more carnivorous bear.
Giant short-faced bear–Arctodus simus
The giant short-faced bear ranks up there with mammoths, mastodons, ground sloths, and saber-tooths as among one of the most spectacular creatures of this era. Studies suggest it lived by aggressive scavenging. It’s extremely acute sense of smell detected blood from a great distance. Then, the beast would relentlessly trot toward the source of the appetizing odor, and its sheer size would intimidate the partially satiated carnivore that actually made the kill into surrendering the carcass. Arctodus simus fossils are more common in western fossil sites, but a few have been discovered in the southeast, proving it did occur here, at least sporadically. An Arctodus simus skeleton rested in the Fern Cave system in Jackson County, Alabama which borders northwestern Georgia, until it was discovered by cavers in 1970. In addition a number of teeth from this species have recently been discovered in north Florida fossil sites, and some Arctodus simus material was also discovered in Virginia.
Grizzly bear–Ursus arctos
Welsh cave in Kentucky yields grizzly bear fossils dating to about 12,000 BP. This is the easternmost known occurrence of this species. Grizzly bears roam hundreds of miles, so it’s likely if they lived in Kentucky then that they must have entered Tennessee. But the lack of grizzly bear fossils in other southeastern states suggests they never penentrated the region in significant numbers. Still, I believe a few irregular stragglers may have wandered into what’s now north Georgia. It may be that the existence of 3 or 4 other species of bears prevented grizzly bears from colonizing much of the southeast during the Pleistocene, and then man arrived, creating another obstacle blocking their migration into the region. Grizzly bears are a relatively recent addition to North America’s mammalian fauna, but they did live on the continent prior to the LGM, 30,000 years BP. They’re the same species as the Eurasian and Alaskan brown bears.
Pleistocene Bears of Southeastern North America
Nothing demonstrates wilderness more than a robust population of free roaming bears. During the Pleistocene before people were around to kill them and destroy their habitat, there must have been tens of thousands of bears living within the boundaries of what today is Georgia. It’s possible that 5 different species could have been found here in the same time span, though we can be more sure there were at least 3 sharing the same range. Today, only 1 species of bear resides in Georgia–an estimated 5100 black bears still roam the mountains, the Okefenokee Swamp, the Altamaha and Ocmulgee river bottoms, and Houston County. Occasional stragglers leave these last strongholds and raid urban dumpsters and suburban bird feeders, but these occurrences are rare. One study of Georgia bears determined that suitable habitat can support 1 bear for every 3 square kilometers. That means ideally, Pleistocene Georgia hosted a population of 30,000-40,000 bears. (*Georgia is about 60,000 square miles. 1.86 square miles =3 square kilimeters. Moreover, during stadials Georgia’s land mass increased by about 10,000 square miles due to the fall in sea level.)
Here’s a review of every known bear species that lived during the Pleistocene in southeastern North America.
Black bear–Ursus americanus
Ursus abstruscus is the probable evolutionary ancestor of American and Asian black bears which once consisted of a geographically continuous population. Glacial ice separated the two populations at the beginning of the Pleistocene, resulting in two different species. Bjorn Kurten notes that Pleistocene black bears grew as large as modern day grizzlies. I believe Pleistocene black bears were larger and fiercer than their modern day descendents because they had to survive confrontations with saber-tooths, giant panthers, jaguars, and packs of dire wolves. Cavers and scientists discovered black bear fossils at Ladds and Kingston Saltpeter Cave in Bartow County, and the Isle of Hope Site in Chatham County. They’re also commonly found in Florida fossil sites but only a few have been recorded from South Carolina.
Florida spectacled bear–Tremarctos floridanus
Now extinct, this was likely the second most common species of bear in southeastern North America during the Pleistocene. Only 1 specimen has ever been recovered in Georgia (at Ladds), but its fossils have commonly been found in Florida and South Carolina. It’s thought of as primarily a vegetarian, but a recent study of Pleistocene bears concluded that all were opportunistic omnivores that would eat anything they could obtain. Tremarctos’s range in the late Wisconsinian Ice Age seems to have been restricted to the southeast. During warm interglacials it expanded as far north as Kentucky. It probably just lived in the coastal plain of Georgia and South Carolina as well as Florida during colder climatic stages.
Lesser short-faced bear–Arctodus pristinus
It’s unclear from the fossil record whether this species co-existed with its larger cousin, the giant short-faced bear, or was simply ancestral to it. Its fossils have only been recovered from a few eastern sites in Florida, South Carolina, Maryland, and West Virginia. Teeth attributed to this species overlap in size with those of Arctodus simus. Florida fossils of this species, including those from Leisey Shell Pit, indicate this animal lived from the early to mid-Pleistocene (~1.8 million-300,000 BP), whereas giant short-faced bear fossils in Florida date to the late Pleistocene (~300,000-~11,000 BP). However, fossils of the lesser short-faced bear were found in South Carolina sediments thought to date from the Sangamonian Interglacial (~132,000-~118,000 BP) which is also considered late Pleistocene. These South Carolina specimens haven’t been radiometrically dated, so no one knows exactly how old they are. Perhaps this species did survive as a relic species in some geographical locations until the megafauna extinction. Arctodus pristinus is considered more of a general feeder; Tremarctos floridanus a more herbivorous species; Arctodus simus a more carnivorous bear.
Giant short-faced bear–Arctodus simus
The giant short-faced bear ranks up there with mammoths, mastodons, ground sloths, and saber-tooths as among one of the most spectacular creatures of this era. Studies suggest it lived by aggressive scavenging. It’s extremely acute sense of smell detected blood from a great distance. Then, the beast would relentlessly trot toward the source of the appetizing odor, and its sheer size would intimidate the partially satiated carnivore that actually made the kill into surrendering the carcass. Arctodus simus fossils are more common in western fossil sites, but a few have been discovered in the southeast, proving it did occur here, at least sporadically. An Arctodus simus skeleton rested in the Fern Cave system in Jackson County, Alabama which borders northwestern Georgia, until it was discovered by cavers in 1970. In addition a number of teeth from this species have recently been discovered in north Florida fossil sites, and some Arctodus simus material was also discovered in Virginia.
Grizzly bear–Ursus arctos
Welsh cave in Kentucky yields grizzly bear fossils dating to about 12,000 BP. This is the easternmost known occurrence of this species. Grizzly bears roam hundreds of miles, so it’s likely if they lived in Kentucky then that they must have entered Tennessee. But the lack of grizzly bear fossils in other southeastern states suggests they never penentrated the region in significant numbers. Still, I believe a few irregular stragglers may have wandered into what’s now north Georgia. It may be that the existence of 3 or 4 other species of bears prevented grizzly bears from colonizing much of the southeast during the Pleistocene, and then man arrived, creating another obstacle blocking their migration into the region. Grizzly bears are a relatively recent addition to North America’s mammalian fauna, but they did live on the continent prior to the LGM, 30,000 years BP. They’re the same species as the Eurasian and Alaskan brown bears.
